Historically, most hand tools include an opening/socket in the metal neck of the work piece head into which a wooden handle is inserted and fixed by means of friction or by fasteners such as rivets, screw, nails, collars, or the like. The metal socket in the head was needed to provide adequate strength at the connection to allow the wooden handle to function while resisting collapse when subjected to bending or torsional stress.
The length of the socket can be modified during manufacture depending on the amount of stress for the desired operation, the length of the shovel handle, and the quality of the wood in the shovel handle. Further, the head can be produced either by stamping and forming metal sheet stock for light duty applications or by using a billet and forging a heavy duty blade for heavy duty application. In virtually all operations whether the shovel blade was made from very thin metal for very low priced and light duty work, or forged from a billet to produce a heavy duty blade, the handle socket is formed by rolling the sheet or forged stock into a conical section. The conical section is prevented from opening by using metal to resist deflection or by either welding the edges together or bolting through the handle shaft stock so that the conical section would not spread out or open up when load was applied on the handle.
The sockets can be either straight or curved along their length. The straight sockets are straight from the opening which will accept the wood handle to the connection or junction of the tool blade. The curved sockets are curved near the smallest point of the socket section so as to create a desired angle between the plane of the blade and the axis of the shovel handle. The strength of the connection is increased when the wooden handle fills the entire volume of the socket. This wood filler helps to resist a compressive failure of the metal conical section when the tool is used as a pry in either digging or actually prying. This failure will occur on every quality tool at a relatively low load level if a core is not inserted which has adequate compressive strength to prevent the collapse of the conical tubing section which has been created out of sheet stock or by forging.
It has been found that fiberglass handles are preferable to wood handles for many reasons, including the fact that fiberglass has a more desirable strength to weight ratio. Most fiberglass handles are produced from a thermosetting process which is irreversible, that is, it cannot be softened by the re-application of heat. It is difficult and costly to attempt to machine the fiberglass to be inserted in a socket which has an angle or curve as above described.
Therefore, there is a need for an improved connection assembly between the handle and the head of a hand tool.